Improvement in countersinks



UNITED STATES PATEW SEWALL L. ABBOTT, OF DEERING, MAINE.

IMPROVEMENT IN COUNTERSINKS.

Specication forming part of Letters Patent No. 117,237, dated July 25,1871.

'o all whom it may concern:

Be it known that I, SEWALL L. ABBOTT, of Deering, in the county ofCumberland and State of Maine, have invented a new and useful IniprovedCountersink; and I hereby declare the following to be a full, clear, andexact description of the saine, reference being had to the accompanyingdrawing forming part of this speciica-tion, in which- Figure 1 shows aback side view of the countersink. Fig. 2 shows a side or edge view.Fig. 3 shows a section of the lower part of the tool, designated at a,to illustrate the form of the curve.

Same letters show like parts.

The general purpose of Iny invention is to show Van improved form oftool for cutting' depressions for the reception of screw-heads, &c.

The part b of the shank shows that end of the cutting-tool made squarewhich is designed to enter and be fastened into the socket of a bit orother tool for giving rotation to the countersink, so as to enable it tocut such a hole or depression as may be desired. c shows the stock,which may be round or rectangular. The portion of the tool upon whichthe cutting-edges are made and from which the point is formed is bestseen in Fig. 3. This would form an oval if the curve Were completed. Theportion upon which the This is produced by cutting or :filing down theedges inja taper form, as illustrated. The inner edge e is thecutting-edge, or the one that rims out the hole made for the receptionof the screw-head. The taper back from the point d enables the tool tocut recesses of various sizes, as may be desired, and to further thisobject the gaugefmarks f are cut and applied to the back or convex partof that portion of the tool seen in section in Fig. 3. With this theuser has only to determine the diameter of the desired recess he Wishesto cut, and to ascertain which gauge or mark exhibits such diameter, andthen to apply the tool till the gauge of the requisite diameter is on alevel with the surface of the wood. The tapering cutting-edges e arealso, as will be observed, slightly concave or curved inwardly. Thisenables the tool to perform its work without breaking out the bers ofthe wood in the hole, and thus it makes a smooth surface or cut.

Vhat 1 claim as my invention, and desire to secure by Letters Patent,is-

The countersink, constructed as herein described, that is, having theoval-shaped cutting portion, seen in section in Fig. 3, the taperingpoint, the inner cutting-edge c, the point d, and the gauges f, asherein set forth.

Portland, April S, 1871.

SEVVALL L. ABBOTT.

Witnesses:

WILLIAM HENRY CLIFFORD, GEORGE E. BIRD.

